Method of finishing flat stock



Dec. 21, 1965 J. Ross METHOD OF FINISHING FLAT STOCK Filed Nov. 27, 1962 l #law o 4 6 0 7N 7 DOA ,d U 9 4 a V s a a m Awa 4 w o ru/ 6 2 O @di s 6MM @fun n f O 9 4% N f@ g W 5 L '01 n, z M 6 NUE b Mh Q O 8 W 6 United States Patent O 3,224,147 METHOD F FINISHING FLAT STOCK John Ross, Southfield, Mich., assignor to Midwest Supply and Manufacturing Company, Ferndale, Mich., a corporation of Michigan Filed Nov. 27, 1962, Ser. No. 240,247 13 Claims. (Cl. 51-281) The present invention relates to an improved method for the abrasive finishing of fiat stock, such as metal sheets, from end to end thereof in a manner to avoid the production of transverse shadow lines or visible high-light marks on the finished sheet. More particularly, the invention concerns a method involving the use of a fiat stock finishing machine of the abrasive belt and billy roll type, the method relating to the manipulation of its billy roll in the finishing operation to eliminate the possibility of occurrence of the shadow lines or marks mentioned above.

In the operation of conventional finishing machines of this type, in which fiat metal sheets are advanced by driven pinch rolls into the bite between a backing or so-called billy roll and a high speed abrasive belt trained around a contact roll or drum directly above the backing roll, the leading edge of the sheet initially engages the abrasive belt just prior to passing into the nip or bite of the belt and the backing or billy roll. This has the effect of causing the sheets leading edge to tend to shave the granular particles of the belt on a transverse line across its width, i.e., parallel to the belt contact roll aXis. The result is that the disturbed grain of the belt, in its succeeding polishing contact with the sheet, tends to, by reason of the irregularity of abrasive particle distribution, leave visible high-light marks or shadow lines on the sheet. The same effect is caused at the trailing edge of the sheet supported by the billy roll in passing beneath the belt, i.e., another disturbance of the belt grain takes place. The operations embraced in the method of the present invention eliminate these possibilities, resulting in the production of finished sheets not subjected to the visible effects referred to.

It is an object of the invention to provide a method including steps in which the supporting of the sheet stock by the billy roll is successively shifted from an initial position in which its aXis is disposed in forwardly offset relation to the axis of the belt contact roll, i.e., in the direction of advance of the sheet by the pinch rolls, to a rearwardly disposed offset position relative to the belt contact roll axis after the sheet has passed the belt, without shaving contact with the latter. Thus the sheet will ride up upon the billy roll in the forwardly disposed position of the latter, having first passed the vertical plane of the belt Contact roll axis, and, the billy roll being then translated to the rear as polishing on the sheet proceeds, the rear end of the sheet will pass the vertical plane of the belt contact roll axis without exerting a parting shaving action on the belt grain.

Another object is to provide an improved fiat stock finishing method of the type described, in which a shift of the support by the billy roll forwardly to rearwardly and return forwardly is .accomplished automatically, as by means herein shown as pneumatic, although hydraulic, electrical, mechanical and other equivalents, or combinations thereof, may be substituted, and in which the automatic control is governed by the sheet itself.

3,224,147 Patented Dec. 21, 1965 ICC A still further object is to provide a method as described, carried out by equipment in which the sheet is advanced toward the abrasive belt and billy roll by a conventional type of driven pinch roll structure, and discharged from the finishing belt by similar driven pinch roll means on the opposite longitudinal or forward side of the belt, in which the control of the automatic control of the shifting of the billy roll in the desired manner originates at a control unit adjacent the first named pinch rolls. As shown herein, the control is photoelectrically derived from the traveling sheet itself to govern the action of the billy roll through illustrative electrical circuitry. However, it is to be understood that other types of billy roll actuation than through electrical agencies are contemplated, just as are equivalents of the illustrated pneumatic provisions.

Yet another object is to provide an improved method in which the control of the supporting of the sheet may be optionally arranged for either a single pass, unidirectional finishing stroke of the sheet, or for a reversing, back-andforth polishing stroke.

Generally, it is an object of the invention to provide a method which is performed entirely automatically to insure the finishing of sheet metal stock without the occurrence of shadow lines or high-lights occasioned by the shaving of the grain of an abrasive member by either the leading or trailing edge of the metal sheet upon entering or leaving the bite of the abrasive member and a coacting billy roll. In addition to avoiding the undesirable marking of the finished sheet, a longer life of the finishing belt is made possible by avoiding the grain shaving action on the belt by the edges of the sheet.

The foregoing as well as other objects will become more apparent as this description proceeds, especially when considered in connection with the accompanying drawings illustrating the invention, wherein:

FIG. 1 is a highly schematic view showing suggested components for the control of the shifting of the billy roll of a fiat stock finishing machine on which the method is carried out; and

FIG. 2 is a schematic wiring diagram of electrical circuitry responsive vto certain photoelectric sensing components of FIG. 1 to control the position of the billy roll.

Referring to FIG. l of the drawings, the reference numeral 10 generally designates the high speed abrasive finishing unit for the polishing of the top surface of a metal sheet S of predetermined width and length, this sheet being forwarded to the abrasive unit 10 in a conventional manner by a set of feed-in pinch rolls 12 arranged in vertically opposed pairs in longitudinally spaced relation to one another in the direction of feed of the sheet S, shown by the arrow in FIG. 1. Upon leaving the abrasive finishing unit 10, the sheet S conventionally enters another set of discharge pinch rolls 14 which are located in pairs relative to one another, like the feed-in rolls 12, 14 and are also driven positively by conventional reversible motor means (not shown).

As in conventional flat stock finishing machines, the sets of pinch rolls 12 may be unidirectionally driven for a single passing of each sheet in the direction of the arrow of FIG. 1, or may be reversibly driven for multiple passes prior to discharge by the set of rolls 12; and the invention contemplates corresponding control of the billy roll shifting provisions, to be described, consistent with either type of stock feed to accomplish the purposes and vice versa willv not exceed two inches.

'a contact-roller 18, and suitably driven at a further upper roll (not shown) at a high linear speed. However, insofar as the present invention isconcerned, the

-unit might be `any conventional high speed rotary drum type.

The billy roll of the apparatus is designated r20, and the invention contemplates the` successive Vlongitudinal shifting thereof from a position shown in solidline in FIG.- 1, as the leading edge of the sheet S approaches vcontact roller'18, to the dotted line position, and vice versa. In the solid line position,'the axis of the billy roll 20 is offset Vforwardly of the vertical plane through `the axis of contact roller 18. In the dotted line position `rthe billyroll axis is offset rearwardly of that plane, in reference tothe direction of sheet feed in both instances.

It is to be understood that the position of billy roll 20 in its two positions relative to the abrasive belt roller axis is exaggerated for the purpose of clarity. Actually, the shifting stroke of the billyl roll from front to rear However, this is sufficient for the purposesy of the invention, and willv permit a -tip-to-tip or end-to-endy polishing action on thesheet S without leaving perceptible shadow or high-lights on the sheet.

This is because of the fact that on the infeed stroke'f 'of "sheet S, with billy roll Z0-in the solid line position of FIG. 1, the forward edge of the sheet will, without significant edge engagement with the belt 16 and result- -ant shaving action on the latter, travel under the belt "and'contact roller-'18, then ride up over the crown of `billy roll 20 as to cause grinding pressure to be applied.

On the other hand, with billy roll` 20 shifted to the rear, dotted line position of FIG. 1 as the polishing proceeds, andafter the leading end of sheet S has entered "the nipof the discharge pinch roll set 14, the billy roll 20 continues to support the sheet until the rear edge of Vthe latter has passedthe'reover,` butV not as' the rear sheet edge departs 'from belt 16;so vthat a second shaving 1action on abrasive belt 16'is avoided. It is to be emphasized that the displacement of billy roll'20 on either side of the vertical plane of the axis of contact roller '18 is very slight; and a support for the application of .highly vuniform grinding pressure is afforded, by the means'to be described, when vthe billy roll is in either iposition, as well as the transitional phase "when the billy roll shifts from front to rear (or from rear to frontv in the event a reversing stroke is to be imparted to sheet S). If needed (as is unlikely), simple provision may be made to guide the billy roll for a stroke which is-not 'strictly rectilinear, in order to achieve a` uniformity of grinding pressure of the greatest possible precision. As herein illustrated, in order to effect the shifting of billy roll'20, it is journaled on a supporting' structure generally designated`22 in FIG. 1, which will maintain gle stroke operation.

friction support roller 34 upon which a bottom guide 36 of the billy roll actuator member 24 may ride. Other than in the fact that the billy roll pick-up unit 28 will sustain the billy roll 20 for its desired reciprocatory shifting action, said unit is conventional. Provision may be made, as by an adjustable stop device 38, to limit as desired the extremes of the shifting action of the billy roll, as will be described.

The billy roll transfer unit 26 is shown schematically in FIG. 1 as comprising a pneumatic cylinder 40, of the plunger to which the billy roll actuator member 24 is pivotally connected. Pneumatic pressure is applied to the opposite ends of cylinder 40 through lines 42 from a conventional four-way, solenoid-actuated valve 44, the intake to which may be controlled by a master'valve 46. Valve 44' is"operated to reverse the fluid flow in lines 42 by means of ay solenoid 48 appearing in FIG. 2 and conventional return spring (not shown). Master valve 46 may` be considered illustrative of suitable means by which the speed of the reversing stroke of the plunger of cylinder' 40 may be governed as desired.

Again referring to FIG. l, the sheet S itself controls the automatic energization and de-energization of the solenoid 48 (hence the reversing of a flow to pneumatic cylinder 40) through the agency of a photoelectric unit 50 `including a light source 52 normally projecting a 'beaml B down through the space between vertically arranged'pairs of the sheet feed-in pinch rolls 12, this beam energizing a suitable photocell component S4 of photoelectric unit 50 in a known manner.

- Similarly, when a reversing stroke operation of the apparatus is contemplated, recourse is had to a second photoelectric unit 56 including a light source 58 adapted to project the beam B to a photocell device 60 in the Zone between the discharge pinch roll sets 14.

The billy roll transfer unit '26has been identified as a pneumatically actuated one.l However, those skilled in the `art will appreciate that a hydraulic cylinder unit could also be employed, or an 'electrically actuated one, or even a mechanically operated one having appropriate connections to the billy roll actuator 24. The important thing is that'the position ofy billy roll 20 in its'vertical relation to the belt contact roller 18 shall be substantially uniformly maintained in the longitudinally shifting of a billy roll to and from the opposite sides yof roller 18.V If greater uniformity of grinding pressure is required to insure an absolutely uniform grinding depth, it is contemplated that supplemental billy roll guide pnovisions may be made, such as lwill produce a stroke'of the billy roll which is arcuate in an extremely mild degree.

Now referring to FIG. r2 of the drawings, the reference numeral 62 designates a normally open contact of a relay vv(otherwise not illustrated) which is closed when the light beam B (FIG. 1) is interrupted by the forward end of the sheet S ventering the pinch roll set 12. Photocell device 54 of the photoelectric unit`5t) then causes the closing of contact 62. This is accomplished through asuitable amplification and relay circuit in the unit'50,-such as will suggest itself to those having ordinary skill in the art, hence not requiring further illustration or description here.

`and b the latter 0f which is closed when switch 64 is in the normal position shown in solid line inFIG. 2 for sin- In this setting of the switch only the photoelectric unit 50 and the contact 62 responsive thereto, plus relay means to be described, are involved. When the switch 64 is set for reversing operation of the apparatus, the `switch contact a is closed (dotted line position in FIG; 2); andlthe control'circitrythenalso'includes in addition to other relay means to be described, a normally open contact 66 of a relay (otherwise not shown) which is responsive to the beam B ofthe discharge side photoelectric unit 56.

In the operation of the electrical components involved in the single stroke setting of reversing switch 64, with the latter in the solid line position of FIG. 2, a circuit is completed from an electrical lead 68 supplied (when the photoelectrically responsive contact 62 is closed) from a standard on-off switch 70 wired to a line lead 71. This circuit includes the switch contact b, a lead 72, the photoelectric contact 62, and a rst timing relay 74 connected to a return line lead 76. A contact 74 of timing relay 74 is adapted (when closed after a delay representing the time it takes for the leading edge of sheet S to enter the discharge pinch rolls 14) to complete a circuit between leads 68, 76 through a lead 78 and the coil of the valve solenoid 48 which controls the pneumatic transfer cylinder 40 for one direction of pneumatic flow.

A similar circuit is, upon closure of photoelectric contact 62, completed through a control relay 80. The contact 80 of control relay 80 closes instantaneously upon energization of the latter, thus energizing the coil of a second time delay relay 82 when the first delay relay contact 74' closes, and the contact 82 of relay 82 is then instantaneously closed. This contact delays in opening until the trailing edge of sheet S passes the vertical plane through the axis of belt contact roller 18. While closed, the timing contact 82 establishes a solenoid holding circuit through a lead 84 and lead 78 to solenoid coil 48.

The two photoelectric units 50 and 56 are shown in FIG. 2 as Wired between the leads 68 and 76 in parallel with the relay and other provisions described above.

Thus, with the billy roll in its normal initial position on the forward or discharge side of the belt contact roller axis (solid line in FIG, l), as the sheet S passes through the feed-in or entrance set of pinch rolls 12 it trips the beam B of photoelectric unit 50, which causes a closure of the photoelectrically responsive Contact 62. This energizes the first delay relay 74, which commences to time out.

The location of photoelectric unit 50 in relation to belt contact roller 18 and the remainder of the apparatus is determined by the linear rate of feed of the sheet S. Accordingly, the leading edge of the sheet travels under contact roller 18 and rides up over the crown of the forwardly positioned billy roll 20, exerting grinding pressure on the sheet.

First time delay relay 74 times out as the leading edge of the sheet S reaches the set of discharge pinch rolls 14 and a feeding grip has been established by the latter on the sheet. As contact 74 closes the coil of the valve solenoid coil 48 is energized. This causes valve 44 to deliver fluid through a line 42 to the cylinder 40 which will cause the latter to draw the billy roll actuating mernber 24 and billy roll 20 to the right from the solid to the dotted line position of FIG. 1, the r-oll maintaining grinding pressure in so moving.

The contact 80' of control relay 80 closes upon the energization of the latter, and when the first delay relay contact 74' closes, thereby energizing the second time delay relay 82, whose contact 82 instantaneously closes to maintain the four-way valve solenoid 48 energized in a circuit sealed around the timing relay contact 74.

After the trailing edge of the sheet S passes the beam B of photoelectric unit 50, the beam is re-established to photocell device 54, with the result that the photoelectrically responsive contact 62 reopens. First delay relay 74 and the control relay 80 are de-energized, opening the respective contacts 74 and 80. This de-energizes the coil of second time delay relay 82. The contact 82 of relay 82 delays in opening until the trailing edge of sheet S passes the center line of belt contact roller 18, whereupon the valve solenoid 48 is de-energized. The attendant reversal of fluid flow to the cylinder 40 causes the billy roll actuator 24 and billy roll 20 to be returned forwardly across the axis of roller 18 to its original position to await a similar cycle involving the next sheet to be nished in a one-pass operation.

With the switch 64 set to the dotted line position of FIG. 2 for a reversing operation, the sequence of events for the forward stroke (left in FIG. l) is the same as described above, save for the fact the forward contact 86 of a conventional motor starter (not shown, but conventionally wired in the circuitry for the usual reversing motor drive for the pinch roll sets 12 and 14) is closed, rather than the b contact of reversing switch 64. The forward circuitry is established through lead 68 to contact 86, thence through the various photoelectric contact and relay provisions described above in connection with onepass operation.

After the forward pass of sheet S, the reverse contact 88 of the motor starter closes, this contact being wired to the contact a of switch 64. Since the contact 66 of the discharge side photoelectric unit 56 is closed by the sheets interruption of the beam B', the result is the energization of a third time delay relay 90 connected between contact 66 and the return line lead 76.

It is to be borne in mind that just before the commencement of the reverse stroke to the right the valve controlling solenoid 44 is de-energized and the billy roll 20 is in the solid line position (FIG. l) to the left of roller 18.

The delay relay 90 has simultaneously acting contacts 90' and 90 which are, respectively, normally closed and open when the relay is de-energized and, as operated together, they delay in respectively dropping out and cutting in upon de-energization of the relay 90. Contacts 90 and 90" are both connected to the starter reversing contact 88, and are also both adapted to complete circuits through a lead 92 and a fourth timing relay 94 to the line lead 76, thus to initiate the reverse drive of pinch roll sets 12 and 14. The normally closed contact 94 of relay 94 is adapted to complete a further circuit through leads 96 and 78 and solenoid 48, thence to the return line lead 76.

Accordingly, with contacts 88 and 66 closed (the former by automatic circuit action and the latter as the result of interruption of photocell beam B), the result is to energize third timing relay 90 and, in turn, the relay 94. While the contact 94 of the latter remains closed in its timing out period, the solenoid 48 is energized and billy oll 20 is shifted to the right to the dotted line position of Relay contact 94 times open as the sheet S enters the right-hand pinch roll set 12 when, as the result of de-energization of solenoid 48 upon opening of Contact 94', the billy roll shifts to the left beneath sheet S, in which position it remains to await the next forward stroke.

When the left-hand photocell beam B is restored upon rightward movement of the sheet, the photo-electrically responsive contact 66 re-opens to de-energize relay 90. Relay 94 becomes energized after the delay of contact 90 in closing, and its contact 94 `delays in re-closing until after the trailing edge of the rightward moving sheet S passes the center line of belt contact roller 18, and after the reversing contact 86 has automatically taken over for a forward stroke to the left, as previously described.

The device 38 appearing in FIG. 1 is employed to determine the distance of the longitudinal stroke of the billy roll 20, as well as the position of the billy roll in reference to the centerline of contact roller 18 in either the forward, solid line position of FIG. l or the rearward, dotted line position. That is, the finishing of certain types of sheet may make it desirable that the billy roll axis be closer to the contact roller axis in the former position than in the latter, or vice versa; or it may be desirable that the sheet have a greater or lesser period of time in which it is un` supported by the billy roll in one or the other of the positions of the latter.

Therefore, the device 38, as schematically shown in FIG. 1, may comprise a suitable abutment or lug 97 carried by the billy roll actuator 24, along with adjustable means `engageahle with opposite sides of such lug to adjustably limit the to-and-fro movement of the billy roll. As shown, such means comprises a support 98 suitably mounted for adjustment in the direction of movement of yactuator 24, the adjustment being under actuation of a threaded stem 100 under manipulation of a hand wheel 101, the stem being appropriately journalled for rotation and held against axial movement. Support 9S in turn has opposed stops 102 mounted thereon for slidable adjustment toward and from one another on the support. Such adjustment may be eected by a reversely threaded screw member 104 manipulated by a hand wheel 106, movement of the screw 104 also being prevented in the axial direction.

The apparatus and its controls are extremely simple and inexpensive, yet reliable and capable of being installed 4readily in various types of physical embodiments to a billy roll type of fiat stock finishing machine.

Elimination'of local physical engagement of the lleading and trailing edges of the sheet with the abrasive member of the finishing unit 10 eliminates the destructive shaving action on the abrasive of the unit with resultant increased belt life, and also eliminates the undesirable shadow lines or high-lights on the finished stock which have heretofore been considered inevitable in equipment of this type.

What I claim as my invention is:

1. A method of finishing fiat sheet stock, comprising feeding the stock flatwise past a rotatively driven abrasive supporting member in a plane paralleling the rotative drive axes of the member for a finishing operation on said stock by said member, and supporting said stock adjacent said member, at the commencement of the finishing operation, only in a zone just forward of the drive axis of said member, in respect to the direction of feed of the stock, with the leading edge of the stock unsupported as the latter initially engages said member.

2. A method of finishing fiat sheet stock, comprising feeding the stock fiatwise past a rotatively driven abrasive supporting member in a plane paralleling the rotative Vdrive axis of the member for a finishing operation on said stock by said member, supporting said stock adjacent said member, at the commencement of the finishing operation, only in a zone just forward of the drive axis of said member, in respect to the direction of feed of the stock, with the leading edge of the stock unsupported as the latter initially engages said member, and then shifting the supporting of the stock to a position rearward of said axis as finishing proceeds.

3. A method in accordance with claim 2, in which change in the supporting of the stock is carried out in timed relation to the feeding movement of the stock.

4. A method of finishing fiat sheet stock, comprising feeding the stock fiatwise past a rotatively driven abrasive supporting member in a plane paralleling the rotative drive axis of the member for a finishing operation on said stock by said member, supporting said stock adjacent said member, at the commencement of the finishing operation, only in a zone just forward of the drive axis of said member, in respect to the direction of feed of the stock, with the leading edge of the stock unsupported as the latter initially engages said member, shifting the supporting of the stock to a position rearward of said axis as finishing proceeds, and then returning the supporting of the stock forwardly to the initial position after the trailing edge of the sheet has passed the axis of said member.

5. A method in accordance with claim 4, in which change in the supporting of the stock is carried out in timed relation to the feeding movement of the stock.

6. A method of finishing fiat sheet stock, comprising feeding the stock fiatwise past a rotatively driven abrasive supporting member in a plane paralleling the rotative drive axis. of the member for a finishing operation on said stock by said member, supporting said stock adjacent said member, at the commencement of the finishing operation, only in a zone just forward of the drive axis of said member, in respect to the direction of feed of the stock, with the leading edge of the stock unsupported as the latter initially engages said member, and controlling the positioning of the supporting of the stock in response to signal from said stock in the feed of the latter.

V7. A method of finishing a fiat sheet under the action of -a rotatively driven finishing member, comprising feeding the sheet fiatwise in a plane paralleling the rotative drive axis of said member in the finishing engagement with the latter, and supporting the sheet at a point located forwardly relative to said drive axis, in reference to the direction of sheet feed, to hold the sheet against said member after the sheet takes engagement with said member, and in the absence of a corresponding supporting of the sheet at the same time on the opposite side of said drive axis.

8. A method of finishing a fiat sheet under the action of a rotatively driven finishing member, comprising feeding the sheet fiatwise in a plane paralleling the rotative drive axis of said member in the finishing engagement with the latter, supporting the sheet at a point located forwardly relative to said drive axis, in reference to the direction of sheet feed, to hold the sheet against said member after the sheet takes engagement with said member, and shifting the supporting of the sheet in the opposite direction relative to the nishing member drive axis prior to termination of the nishing, whereby the leading and trailing edge of the sheet have diminished support in engaging and disengaging said member.

9. A method in accordance with claim 8, in which change in t-he supporting of the sheet is carried out in timed relation to the feeding movement of the sheet and in response to signal originated by the latter.

10. A method of finishing a fiat sheet under the action of a rotatively driven finishing member, comprising feeding the sheet fiatwise in a plane paralleling the rotative drive axis of said member in the finishing engagement with the latter, supporting the sheet at a location located forwardly relative to said drive axis, in reference to the direction of sheet feed, to hold the sheet against said member after the sheet takes engagement with said member, continuing the supporting of the sheet at said location as finishing progresses, and shifting the supporting of the sheet in the opposite direction relative to the finishing member drive axis prior to termination of the finishing, whereby the leading and trailing edges of the sheet have diminished support in engaging and disengaging said member.

11. A method in accordance with claim 10, in which change in the supporting of the sheet is carried out in timed relation to the feeding movement of the sheet and in response to signal originated by the latter.

12. A method of finishing a fiat sheet under the action 'of a rotatively driven finishing member, comprising feeding the sheet fiatwise in a plane paralleling the rotative drive axis of said member in the finishing engagement with the latter, supporting the sheet at a location located forwardly relative to said drive axis, in reference to the direction of sheet feed, to hold the sheet against said member after the sheet takes engagement with said member, continuing the supporting of the sheet at said location as finishing progresses, shifting the supporting of the sheet in .the opposite direction relative to the finishing member drive axis prior to termination of the finishing, whereby the leading and trailing edges of the sheet have diminished support in engaging and disengaging said member, and restoring the supporting of the sheet to its first named relation to said axis upon termination of the finishing of said sheet.

13. A method in accordance with claim 12, in which change in the supporting ofthe sheet is carried out in timed References Cited by the Examiner UNITED STATES PATENTS 590,836 9/1897 Hayes. 1,998,770 4/1935 Shulte 51--76 2,896,379 7/1959 Herrmann 51-216 Kibble 51-78 Herman et a1. 51-215 Peyches 51-283 Kirby 51-283 ROBERT C. RIORDON, Primary Examiner.

FRANK E. BAILEY, LESTER M. SWINGLE,

Examiners. 

7. A METHOD OF FINISHING A FLAT SHEET UNDER THE ACTION OF A ROTATIVELY DRIVEN FINISHING MEMBER, COMPRISING FEEDING THE SHEET FLATWISE IN A PLANE PARALLELING THE ROTATIVE DRIVE AXIS OF SAID MEMBER IN THE FINISHING ENGAGEMENT WITH THE LATTER, AND SUPPORTING THE SHEET AT A POINT LOCATED FORWARDLY RELATIVE TO SAID DRIVE AXIS, IN REFERENCE TO THE DIRECTION OF SHEET FEED, TO HOLD THE SHEET AGAINST SAID MEMBER AFTER THE SHEET TAKES ENGAGEMENT WITH SAID MEMBER, AND IN THE ABSENCE OF A CORRESPONDING SUPPORTING OF THE SHEET AT THE SAME TIME ON THE OPPOSITE SIDE OF SAID DRIVE AXIS. 